Masatoshi Yamazaki

Molecular cloning of a cDNA encoding a novel member of the mouse glutamate receptor channel family

The primary structure of a novel putative subunit of the mouse glutamate receptor channel, designated as delta 1, has been deduced by cloning and sequencing the cDNA. The delta 1 subunit shows 21-25% amino acid sequence identity with previously characterized rodent glutamate receptor channel subunits and thus may represent a new subfamily of the glutamate receptor channel.

Cloning and functional expression of a cDNA encoding the mouse β2 subunit of the kainate-selective glutamate receptor channel

The primary structure of the mouse glutamate receptor beta 2 subunit has been deduced by cloning and sequencing cDNA. The beta 2 subunit has structural characteristics common to the subunits of glutamate-gated ion channels. Expression of the cloned cDNA in Xenopus oocytes yields functional glutamate receptor channels selective for kainate.

Pancreatic vagal functional distribution in the secretion of insulin evoked by portal infusion of D-glucose.

The vagus glucose signal pathway relevant to hepatic portal control of insulin secretion was examined in bilaterally adrenalectomized rats. The increase in the insulin concentration after portal glucose injection was completely blocked by vagotomy of the hepatic branch which is bifurcated from the ventral vagus trunk at the subdiaphragmatic level. At the cervical level, the reduction in the insulin concentration showed no laterality following vagotomy on either side. The insulin response was mainly suppressed by prior section of the branch of the ventral vagus trunk at the celiac level. These results suggest that the hepatic glucose signal evoking insulin release has a specific pathway from the liver to the pancreas, and that there is functional laterality in this pathway in the visceral cavity.

Acute loading with proteins from different sources in healthy volunteers and diabetic patients

To evaluate the effects of protein loading on glomerular filtration rate (GFR), urinary excretion rate of albumin (AER), and plasma concentration of amino acids, 10 healthy volunteers and six diabetics were studied before and after eating tuna fish, egg white, cheese, or tofu. Furthermore, to study the possible role of glucagon, growth hormone (GH), atrial natriuretic peptide (ANP), or kallikrein in the responses of GFR, these substances were measured before and after protein loading. GFR increased significantly (p less than .001) after ingestion of tuna fish. No significant differences were seen between the GFR before and that after ingestion of the other foods. AER was unchanged following protein loading. Plasma concentrations of alanine, glycine, and arginine increased to a greater degree after ingestion of tuna fish than after digestion of the other foods. This result suggests that the response of GFR after protein loading may differ from one protein to another, and that these responses may not be directly mediated by glucagon, GH, ANP, or kallikrein.

d-Glucose anomers in the nucleus of the vagus nerve can depress gastric motility of rats

The infusion of alpha-,beta-, or equilibrated (alpha: 36%; beta: 64%) D-glucose solution in the vicinity of the nucleus of the vagus nerve decreased gastric motility caused by insulin in rats with bilateral adrenalectomy. This effect was not reproduced after vagotomy at the cervical level. Of the 3 forms of D-glucose solution the effect of beta-D-glucose was greatest. The infusion of isotonic NaCl, however, produced no change in the motility. These results suggest that blood beta-D-glucose may predominantly activate a brain mechanism which vagally controls gastric motility at the medullary level.

Changes in water intake following pharyngolaryngeal deafferentation in the rat

The role of afferent information arising from the pharyngolaryngeal region in the regulation of water intake was evaluated in rats. The animals received picric application to the mucosa of either the pharyngolaryngeal or the hard palate region. Water intake of the pharyngolaryngeal treated animals was reduced significantly, while no reduction in water intake was shown in the control and hard palate treated animals.

Hepatic portal injection of glucose elevates efferent sympathetic discharges of interscapular brown adipose tissue

Efferent sympathetic discharges of interscapular brown adipose tissue were recorded after three different concentrations of glucose (138, 277, and 416 mM) and 154 mM NaCl were injected into the portal vein or into the right jugular vein. When injected into the portal vein there was a significant increase in the discharge in response to both concentrations of glucose (277 and 416 mM), whereas only 416 mM glucose solution could cause an increase in the discharge when injected into the right jugular vein. There was no appreciable change in the discharge following the NaCl injections into the portal and jugular veins, and the portal glucose responses in the discharge were abolished by transection of the hepatic branch of the vagus nerve. Since stimulated sympathetic activity has been shown to elevate thermogenesis of the adipose tissue, these findings suggest that vagal glucose signals derived from the portal vein may be involved in the regulation of heat production of this tissue.

Effect of a somatostatin analogue (SMS 201–995) on renal function and urinary protein excretion in diabetic rats

We evaluated the effect of a somatostatin analogue (SMS 201-995) on diabetic nephropathy using urinary albumin excretion as a marker in a streptozocin-induced diabetic unilateral nephrectomized rat model. Nondiabetic rats were injected with either 0.9% sodium chloride (NaCl) (n = 10) or SMS (n = 10). Diabetic rats were also injected with either 0.9% NaCl (n = 10) or SMS (n = 10). The control saline and SMS groups showed significant increases in urinary albumin excretion (UAE) and albumin clearance. The diabetic saline-treated rats showed no significant changes in UAE or albumin clearance. The diabetic SMS-treated rats showed significant decreases in UAE (151 +/- 76 mg/day/kg to 98 +/- 46, P less than .005) and albumin clearance (5.85 +/- 3.34 mL/day/kg to 3.63 +/- 1.73, P less than .01). There was no significant difference in kidney weight between the two control groups, but a significant difference was found between the two diabetic groups (3.35 +/- 0.39 g vs. 2.68 +/- 0.26 g, P less than .001). The results suggest that in early diabetes with renal hyperfiltration and hypertrophy, the administration of SMS may prevent progression to late diabetic nephropathy.

Changes in water intake following hepatic vagotomy in young rats

Changes in water intake after hepatic vagotomy were examined in the body weights of 3 different rats (about 100, 200 and 280 g). The vagotomy reduced water intake only in the 100-g rats.

Glomerular charge selectivity in non-insulin-dependent diabetes mellitus

To elucidate the stage of the charge selectivity defect in diabetic nephropathy, urinary excretions of IgG1 and IgG4 were measured in patients with non-insulin-dependent diabetes mellitus (NIDDM) and healthy controls. The molecular weights of IgG1 and IgG4 were the same but their isoelectric points were different. Therefore, by measuring both urinary IgG1 and IgG4 excretions, the stage of charge selectivity impairment in the nephropathy of NIDDM may be elucidated. Results were expressed as urinary excretion rate (IgG1 ER, IgG4 ER) and compared between diabetic patients with different urinary excretion rates of albumin (AER). IgG4 ER increased to the stage in which AER was more than 10 micrograms/min, whereas IgG1 ER did not increase to the stage of AER between 10 and 100 micrograms/min. This finding suggests that the charge selectivity defect in the kidney of the NIDDM patient is present at the stage when AER is more than 10 micrograms/min.